The present invention relates to a method of communicating the operating conditions of an internal combustion engine.
Control systems are known in which a microcomputer is employed as a feedback control unit for controlling the ratio of the air-fuel mixture supplied to the engine. The feedback control unit receives data related to the concentration of a predetermined component in the exhaust gas by an exhaust gas sensor such as an oxygen concentration sensor (O.sub.2 sensor), and produces a loop feedback signal depending upon an output signal from the O.sub.2 sensor. The feedback control unit, then, corrects the ratio of the air-fuel mixture supplied to the engine depending upon the produced loop feedback signal to control the air-fuel ratio to a desired value.
The control system usually includes a specific output terminal for checking whether the loop feedback signal lies within a predetermined range or not, in order to adjust the feedback control unit. The control system is also equipped with another specific output terminal for an O.sub.2 sensor check signal which is synchronized with the output signal from the O.sub.2 sensor. The O.sub.2 sensor check signal is used for checking the response performance of the O.sub.2 sensor. Furthermore, the control system is sometimes equipped with further output terminals for diagnosing signals which communicate abnormal operations or malfunctions of the engine or of the elements constituting the control system to the mechanic when tuning the engine.
As mentioned above, since the conventional control system is equipped with many specific output terminals and many output buffers, one for each of the various check signals and each of the various diagnostic signals, the control system becomes complicated and expensive to manufacture.